Recently, in the field of communication systems for transmitting various information, owing to development of various communication terminal equipments and data processing systems as well as improvement of service networks of the ISDN (Integrated Service Digital Network), digital broadcasting, etc., transmission and reception of information using portable type equipments replacing fixed type equipments are widely coming into use. There is installed a radio communication module having radio communication function, storage function, etc. in a communication apparatus. Such a radio communication module includes an antenna unit for transmitting and receiving information signals which has an antenna and a changing-over switch, a transmission/reception switching-over unit for switching operational function between transmission and reception, a reception circuit unit having a frequency conversion circuit, a demodulation circuit, etc., a transmission circuit unit having a power amplifier, a drive amplifier, a modulation circuit, etc., and a reference frequency generation circuit unit for providing the reception circuit unit and the transmission circuit unit with reference frequency.
The radio communication module is coming to have higher functions or multiple functions, enabling high-speed communication of various information such as data information, image information, etc., while being required to be reduced in size as well as to have low electric power consumption property so as to be installed in a portable type communication apparatus. Conventionally, the radio communication module is configured using a circuit manufactured under the lumped-constant design, in which a substrate has formed thereon various filters and couplers as well as mounted thereon chip parts such as capacitors and coils. On the other hand, the radio communication module employing the lumped-constant design cannot fulfill above-described demand specification. Thus, generally, the radio communication module is configured using a circuit manufactured under the distributed parameter design, in which a wiring substrate has formed thereon passive elements such as inductors, capacitors, etc. in the film forming manner, and the respective passive elements and mount components are connected through transmission lines such as microstrip lines and strip lines.
FIG. 1 shows the configuration of a conventional high frequency module substrate 100 in which a two-layer high frequency circuit unit 101 is formed in the buildup manner on a four-layer base substrate unit 102 which is formed by the general multilayer print wiring technology. In the high frequency module substrate 100, a first wiring layer 103 and a second wiring layer 104 are formed on a dielectric insulating layer respectively in the pattern forming manner to form the high frequency circuit unit 101, and passive elements such as inductors and capacitors are formed in the first and second wiring layers 103, 104 in the film forming manner by employing the thin-film technology or the thick-film technology, details of which will be omitted. The first wiring layer 103 has formed thereon in the pattern forming manner a transmission line 105 to connect the respective passive elements and lands which is formed under the distributed parameter design.
The high frequency module substrate 100 has power circuits and control circuits formed in respective wiring layers 106, 107, 108, and 109 of the base substrate unit 102 thereof, and the third wiring layer 106 is a fully solid ground layer whose whole surface is formed into ground, details of which will be omitted. In the high frequency module substrate 100, the high frequency circuit unit 101 and the base substrate unit 102 are electrically separated with the ground layer 106 arranged therebetween, which can suppress mutual electrical interference to realize property improvement. In the high frequency module substrate 100, since the ground layer 106 is defined as a ground surface, the transmission line 105 works as a microstrip line.
FIG. 2 shows the configuration of a high frequency module substrate 110 in which a two-layer high frequency circuit unit 111 is formed in the buildup manner on a four-layer base substrate unit 112 which is formed by the general multilayer print wiring technology, in which basic configuration of the high frequency circuit unit 111 and the base substrate unit 112 is similar to that in the high frequency module substrate 100. In the high frequency module substrate 110, a first wiring layer 113 of the high frequency circuit unit 111 has formed thereon in the pattern forming manner a transmission line 115 which is formed under the distributed parameter design, and has formed thereon ground patterns 116a and 116b being kept insulated from the transmission line 115.
The high frequency module substrate 110 shown in FIG. 2 has hollowed patterns 117a, 118a, 119a, and 120a formed at parts of respective wiring layers 117, 118, 119, and 120 of the base substrate unit 112 thereof facing the transmission line 115, which configuration defines no ground surface for the transmission line 115. In the high frequency module substrate 110, employing this configuration, the transmission line 115 works as a coplanar line. In the high frequency module substrate 110, the hollowed patterns 117a, 118a, 119a, and 120a are formed at all the respective wiring layers 117, 118, 119, and 120 of the base substrate unit 112. On the other hand, as a configuration not losing coplanar function of the transmission line 115, the fifth wiring layer 119 may be a fully solid ground layer.
FIG. 3 shows the configuration of a high frequency module substrate 130 in which a high frequency circuit unit 131 having two wiring layers 133 and 134 is formed in the buildup manner on a base substrate unit 132 having four wiring layers 137, 138, 139, and 140 which is formed by the general multilayer print wiring technology, in which basic configuration of the high frequency circuit unit 131 and the base substrate unit 132 is similar to that in the high frequency module substrate 110. In the high frequency module substrate 130, the first wiring layer 133 of the high frequency circuit unit 131 has formed thereon in the pattern forming manner a transmission line 135 which is formed under the distributed parameter design, and has formed thereon ground patterns 136a and 136b being kept insulated from the transmission line 135.
In the high frequency module substrate 130 shown in FIG. 3, the third wiring layer 137 of the base substrate unit 132 is a fully solid ground layer. In the high frequency module substrate 130, the high frequency circuit unit 131 and the base substrate unit 132 are electrically separated with the ground layer 137 arranged therebetween, which can suppress mutual electrical interference to realize property improvement. In the high frequency module substrate 130, since the ground layer 137 is defined as a ground surface, the transmission line 135 works as a ground coplanar line.
FIG. 4 shows the configuration of a high frequency module substrate 150 in which a high frequency circuit unit 151 having two wiring layers 153 and 154 is formed in the buildup manner on a base substrate unit 152 having four wiring layers 157, 158, 159, and 160 which is formed by the general multilayer print wiring technology, in which basic configuration of the high frequency circuit unit 151 and the base substrate unit 152 is similar to that in the high frequency module substrate 110. In the high frequency module substrate 150, the first wiring layer 153 of the high frequency circuit unit 151 has formed thereon in the pattern forming manner a transmission line 155 which is formed under the distributed parameter design, and has formed thereon ground patterns 156a and 156b being kept insulated from the transmission line 155.
In the high frequency module substrate 150 shown in FIG. 4, the third wiring layer 157 of the base substrate unit 152 is a fully solid ground layer. In the high frequency module substrate 150, the high frequency circuit unit 151 and the base substrate unit 152 are electrically separated with the ground layer 157 arranged therebetween, which can suppress mutual electrical interference to realize property improvement. In the high frequency module substrate 150, since the ground layer 157 is defined as a ground surface, the transmission line 155 works as a ground coplanar line.
In the high frequency module substrate 150 shown in FIG. 4, the fourth wiring layer 158 of the base substrate unit 152 has formed thereon in the pattern forming manner a transmission line 161 which is formed under the distributed parameter design, and the fifth wiring layer 159 facing the ground layer 157 with the transmission line 161 arranged therebetween is also a fully solid ground layer. Thus, the high frequency module substrate 150 has the transmission line 161 working as a strip line formed at an inner layer of the base substrate unit 152 thereof together with the transmission line 155 working as a ground coplanar line of the high frequency circuit unit 151.
On the other hand, in the conventional high frequency module, a ground pattern formed on a layer of multiple wiring substrates of, especially, a high frequency signal processing unit alone of a high frequency circuit block is defined as a ground surface to form a microstrip type transmission line, which can improve cost merit as well as effectively utilize substrate area. Since a semiconductor chip and electronic parts are mounted on the surface of a high frequency module, for example, a high frequency module substrate 200 shown in FIG. 5 is arranged.
FIG. 5 shows the configuration of a high frequency module substrate 200 in which a high frequency circuit unit is formed in the buildup manner on a base substrate unit which is formed by the general multilayer print wiring technology, details of which will be omitted. In the high frequency module substrate 200, a surface layer 201 of the high frequency circuit unit shown in FIG. 5 has formed thereon a spiral type inductor element 202 in the film forming manner and a ground pattern 203 enclosing the inductor element 202. The inductor element 202 has its one end connected to a transmission line 204, and has its other end connected to an inner layer circuit of the high frequency circuit unit through via holes, details of which will be omitted.
In the high frequency module substrate 200, the surface layer 201 has formed thereon plural lands 205, 206, 207, and 208 onto which a semiconductor chip, not shown, is to be mounted under the flip chip mounting, as shown in FIG. 5. The first land 205 and the fourth land 208 are lands for ground which are unitedly formed together with ground patterns 209a and 209b respectively, and are connected to a ground pattern formed on a buildup-forming surface of the base substrate unit side through via holes, details of which will be omitted. The second land 206 is a land for DC signals. The third land 207 is a land for RF signals to which one end of the transmission line 204, whose other end is connected to the inductor element 202, is connected. The transmission line 204 is a microstrip type transmission line which defines the ground pattern formed at the base substrate unit side as a ground surface.
In the high frequency module substrate 200, the surface layer 201 has properly formed thereon plural lands, transmission lines, and passive elements such as capacitor elements, register elements, etc. In the high frequency module substrate 200, an antenna element, a coupler pattern, etc. are also formed in the film forming manner, and surface-mount type electronic parts which do not require ground connection are also properly mounted.
In the high frequency module substrate 200 shown in FIG. 5, since a ground pattern is formed on a buildup-forming surface of the base substrate unit side, it becomes possible to form transmission lines for digital signals, etc. in an inner layer, which can realize high density mounting. On the other hand, in the high frequency module substrate 200, a transmission line 210 for DC signals is formed on the surface layer 201, being directed to form a shortest distance from the second land 206. Thus, in the high frequency module substrate 200, the ground patterns 209a, 209b of the lands 205, 208 are separated from the ground pattern 203 of the inductor element 202, in which configuration continuity thereof cannot be maintained. In the high frequency module substrate 200, as has been described above, since the ground patterns 209a, 209b are connected to the ground pattern at the base substrate unit side through via holes, there is raised a problem that resistance components and inductance components of the via affects high frequency property. Furthermore, in the high frequency module substrate 200, since the respective passive elements generates capacitor components between the passive elements and the ground pattern of the base substrate unit side, there is raised a problem that self resonance frequency and Q value of quality factor are reduced, which undesirably deteriorates property.
In the high frequency module substrate 200, since a ground pattern defining a ground surface is formed at the base substrate unit side, and the transmission line 204 is configured as a microstrip type transmission line, thickness of respective layers of the base substrate unit side becomes unequal. Thus, in the high frequency module substrate 200, it is difficult to form a high frequency circuit unit onto the base substrate unit in the buildup manner with high accuracy, which undesirably deteriorates high frequency property.